github: Workaround for Python conflict in macOS image

github: Workaround for Python conflict in macOS image

The Python versions installed in the system image in
`/Library/Frameworks/Python.framework/` have symlinks in `/usr/local/bin/`
that conflict with symlinks that `brew` tries to create, which causes
errors like these:

    ==> Pouring python@3.11--3.11.1.monterey.bottle.tar.gz
    Error: The `brew link` step did not complete successfully
    The formula built, but is not symlinked into /usr/local
    Could not symlink bin/2to3-3.11
    Target /usr/local/bin/2to3-3.11
    already exists. You may want to remove it:
      rm '/usr/local/bin/2to3-3.11'

    To force the link and overwrite all conflicting files:
      brew link --overwrite python@3.11

    To list all files that would be deleted:
      brew link --overwrite --dry-run python@3.11

    Possible conflicting files are:
    /usr/local/bin/2to3-3.11 -> /Library/Frameworks/Python.framework/Versions/3.11/bin/2to3-3.11
    /usr/local/bin/idle3.11 -> /Library/Frameworks/Python.framework/Versions/3.11/bin/idle3.11
    /usr/local/bin/pydoc3.11 -> /Library/Frameworks/Python.framework/Versions/3.11/bin/pydoc3.11
    /usr/local/bin/python3.11 -> /Library/Frameworks/Python.framework/Versions/3.11/bin/python3.11
    /usr/local/bin/python3.11-config -> /Library/Frameworks/Python.framework/Versions/3.11/bin/python3.11-config